Drug-drug interactions in the treatment of HIV infection: focus on pharmacokinetic enhancement through CYP3A inhibition

Involvement of endoplasmic reticulum stress in rifampicin-induced liver injury

Rifampicin is a first-line antituberculosis drug. Hepatocyte toxicity caused by rifampicin is a significant clinical problem. However, the specific mechanism by which rifampicin causes liver injury is still poorly understood. Endoplasmic reticulum (ER) stress can have both protective and proapoptotic effects on an organism, depending on the environmental state of the organism. While causing cholestasis and oxidative stress in the liver, rifampicin also activates ER stress in different ways, including bile acid accumulation and cytochrome p450 (CYP) enzyme-induced toxic drug metabolites via pregnane X receptor (PXR). The short-term stress response helps the organism resist toxicity, but when persisting, the response aggravates liver damage. Therefore, ER stress may be closely related to the “adaptive” mechanism and the apoptotic toxicity of rifampicin. This article reviews the functional characteristics of ER stress and its potentially pathogenic role in liver injury caused by rifampicin.

The FDA-Approved Drug Cobicistat Synergizes with Remdesivir To Inhibit SARS-CoV-2 Replication In Vitro and Decreases Viral Titers and Disease Progression in Syrian Hamsters

Combinations of direct-acting antivirals are needed to minimize drug resistance mutations and stably suppress replication of RNA viruses. Currently, there are limited therapeutic options against the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and testing of a number of drug regimens has led to conflicting results. Here, we show that cobicistat, which is an FDA-approved drug booster that blocks the activity of the drug-metabolizing proteins cytochrome P450-3As (CYP3As) and P-glycoprotein (P-gp), inhibits SARS-CoV-2 replication. Two independent cell-to-cell membrane fusion assays showed that the antiviral effect of cobicistat is exerted through inhibition of spike protein-mediated membrane fusion. In line with this, incubation with low-micromolar concentrations of cobicistat decreased viral replication in three different cell lines including cells of lung and gut origin. When cobicistat was used in combination with remdesivir, a synergistic effect on the inhibition of viral replication was observed in cell lines and in a primary human colon organoid. This was consistent with the effects of cobicistat on two of its known targets, CYP3A4 and P-gp, the silencing of which boosted the in vitro antiviral activity of remdesivir in a cobicistat-like manner. When administered in vivo to Syrian hamsters at a high dose, cobicistat decreased viral load and mitigated clinical progression. These data highlight cobicistat as a therapeutic candidate for treating SARS-CoV-2 infection and as a potential building block of combination therapies for COVID-19.

Clinically relevant enantiomer specific R- and S-praziquantel pharmacokinetic drug-drug interactions with efavirenz and ritonavir

We conducted a clinical study to determine the effect of efavirenz and ritonavir on the pharmacokinetics of R- and S-PZQ in healthy male participants. This was toward evaluating the risk of drug-drug interactions, which may occur after PZQ administration to HIV patients on efavirenz or ritonavir containing regimens. A non-randomized, open-label, single-dose, one sequence crossover study with 2 arms was conducted. We gave 26 healthy volunteers a single oral dose of 40 mg/kg PZQ followed by a daily oral dose of either 400 mg efavirenz or 100 mg ritonavir for 14 consecutive days. On day 14, they ingested a single 40 mg/kg dose of PZQ. We measured plasma levels up to 12 h on day 1 and day 14. Samples were analyzed by LC-MS. Pharmacokinetic analysis was conducted in WinNonlin to determine the primary endpoints (plasma T_1/2 , C_min , and AUC). Efavirenz had a significant effect on the pharmacokinetics of PZQ (p < .05), reducing the AUC by 4-fold (1213.15 vs. 281.35 h·ng/ml for R-PZQ and 5669 vs. 871.84 h·ng/ml for S-PZQ). Ritonavir had no significant effect on R-PZQ but increased the AUC 2-fold for S-PZQ (p < .05) (4154.79 vs. 7291.05 h·ng/ml). Using PZQ in HIV patients needs investigation, as there is a risk of both treatment failure and adverse effects because of induction and inhibition, respectively.

Insights into oral bioavailability enhancement of therapeutic herbal constituents by cytochrome P450 3A inhibition

Herbal plants typically have complex compositions and diverse mechanisms. Among them, bioactive constituents with relatively high exposure in vivo are likely to exhibit therapeutic efficacy. On the other hand, their bioavailability may be influenced by the synergistic effects of different bioactive components. Cytochrome P450 3A (CYP3A) is one of the most abundant CYP enzymes, responsible for the metabolism of 50% of approved drugs. In recent years, many therapeutic herbal constituents have been identified as CYP3A substrates. It is more evident that CYP3A inhibition derived from the herbal formula plays a critical role in improving the oral bioavailability of therapeutic constituents. CYP3A inhibition may be the mechanism of the synergism of herbal formula. In this review, we explored the multiplicity of CYP3A, summarized herbal monomers with CYP3A inhibitory effects, and evaluated herb-mediated CYP3A inhibition, thereby providing new insights into the mechanisms of CYP3A inhibition-mediated oral herb bioavailability.

Corticosteroids in patients hospitalized for COVID-19 pneumonia who require oxygen: observational comparative study using routine care data

OBJECTIVE

To assess the effectiveness of corticosteroids on outcomes of patients with coronavirus disease 2019 (COVID-19) pneumonia requiring oxygen without mechanical ventilation.

METHODS

We used routine care data from 51 hospitals in France and Luxembourg to assess the effectiveness of corticosteroids at 0.8 mg/kg/day eq. prednisone (CTC group) versus standard of care (no-CTC group) among adults 18-80 years old with confirmed COVID-19 pneumonia requiring oxygen without mechanical ventilation. The primary outcome was intubation or death by day 28. In our main analysis, characteristics of patients at baseline (i.e. time when patients met all inclusion criteria) were balanced by using propensity-score inverse probability of treatment weighting.

RESULTS

Among the 891 patients included in the analysis, 203 were assigned to the CTC group. Use of corticosteroids was not significantly associated with risk of intubation or death by day 28 (weighted hazard ratio (wHR) 0.92, 95%CI 0.61-1.39) nor cumulative death rate (wHR 1.03, 95%CI 0.54-1.98). However, use of corticosteroids was associated with reduced risk of intubation or death by day 28 in the prespecified subgroups of patients requiring oxygen ≥3 L/min (wHR 0.50, 95%CI 0.30-0.85) or C-reactive protein level ≥100 mg/L (wHR 0.44, 95%CI 0.23-0.85). The number of hyperglycaemia events was higher for patients with corticosteroids than for those without, but the number of infections was similar.

CONCLUSIONS

We found no association between the use of corticosteroids and intubation or death in the broad population of patients 18-80 years old, with COVID-19, hospitalized in settings non intensive care units. However, the treatment was associated with a reduced risk of intubation or death for patients with ≥3 L/min oxygen or C-reactive protein level ≥100 mg/L at baseline. Further research is needed to confirm the right timing for corticosteroids in patients with COVID-19 requiring oxygen only.

Pharmacogenomics of Antiretroviral Drug Metabolism and Transport

Antiretroviral therapy has markedly reduced morbidity and mortality for persons living with human immunodeficiency virus (HIV). Individual tailoring of antiretroviral regimens has the potential to further improve the long-term management of HIV through the mitigation of treatment failure and drug-induced toxicities. While the mechanisms underlying anti-HIV drug adverse outcomes are multifactorial, the application of drug-specific pharmacogenomic knowledge is required in order to move toward the personalization of HIV therapy. Thus, detailed understanding of the metabolism and transport of antiretrovirals and the influence of genetics on these pathways is important. To this end, this review provides an up-to-date overview of the metabolism of anti-HIV therapeutics and the impact of genetic variation in drug metabolism and transport on the treatment of HIV. Future perspectives on and current challenges in pursuing personalized HIV treatment are also discussed.

Treatments in Covid-19 patients with pre-existing metabolic dysfunction-associated fatty liver disease: A potential threat for drug-induced liver injury?

Obese patients who often present metabolic dysfunction-associated fatty liver disease (MAFLD) are at risk of severe presentation of coronavirus disease 2019 (COVID-19). These patients are more likely to be hospitalized and receive antiviral agents and other drugs required to treat acute respiratory distress syndrome and systemic inflammation, combat bacterial and fungal superinfections and reverse multi-organ failure. Among these pharmaceuticals, antiretrovirals such as lopinavir/ritonavir and remdesivir, antibiotics and antifungal agents can induce drug-induced liver injury (DILI), whose mechanisms are not always understood. In the present article, we hypothesize that obese COVID-19 patients with MAFLD might be at higher risk for DILI than non-infected healthy individuals or MAFLD patients. These patients present several concomitant factors, which individually can favour DILI: polypharmacy, systemic inflammation at risk of cytokine storm, fatty liver and sometimes nonalcoholic steatohepatitis (NASH) as well as insulin resistance and other diseases linked to obesity. Hence, in obese COVID-19 patients, some drugs might cause more severe (and/or more frequent) DILI, while others might trigger the transition of fatty liver to NASH, or worsen pre-existing steatosis, necroinflammation and fibrosis. We also present the main mechanisms whereby drugs can be more hepatotoxic in MAFLD including impaired activity of xenobiotic-metabolizing enzymes, mitochondrial dysfunction, altered lipid homeostasis and oxidative stress. Although comprehensive investigations are needed to confirm our hypothesis, we believe that the current epidemic of obesity and related metabolic diseases has extensively contributed to increase the number of cases of DILI in COVID-19 patients, which may have participated in presentation severity and death.

Novel elvitegravir nanoformulation for drug delivery across the blood-brain barrier to achieve HIV-1 suppression in the CNS macrophages

The use of antiretroviral therapy (ART) has remarkably decreased the morbidity associated with HIV-1 infection, however, the prevalence of HIV-1-associated neurocognitive disorders (HAND) is still increasing. The blood-brain barrier (BBB) is the major impediment for penetration of antiretroviral drugs, causing therapeutics to reach only suboptimal level to the brain. Conventional antiretroviral drug regimens are not sufficient to improve the treatment outcomes of HAND. In our recent report, we have developed a poloxamer-PLGA nanoformulation loaded with elvitegravir (EVG), a commonly used antiretroviral drug. The nanoformulated EVG is capable of elevating intracellular drug uptake and simultaneously enhance viral suppression in HIV-1-infected macrophages. In this work, we identified the clinical parameters including stability, biocompatibility, protein corona, cellular internalization pathway of EVG nanoformulation for its potential clinical translation. We further assessed the ability of this EVG nanoformulation to cross the in vitro BBB model and suppress the HIV-1 in macrophage cells. Compared with EVG native drug, our EVG nanoformulation demonstrated an improved BBB model penetration cross the in vitro BBB model and an enhanced HIV-1 suppression in HIV-1-infected human monocyte-derived macrophages after crossing the BBB model without altering the BBB model integrity. Overall, this is an innovative and optimized treatment strategy that has a potential for therapeutic interventions in reducing HAND.

Prevalence and Patterns of Antiretroviral Therapy Prescription in the United States

Background:

The use of Antiretroviral Therapy (ART) in HIV-infected persons has proven to be effective in the reduction of risk of disease progression and prevention of HIV transmission.

Objective:

U.S. Antiretroviral Therapy (ART) guidelines specify recommended initial, alternative initial, and not-recommended regimens, but data on ART prescribing practices and real-world effectiveness are sparse.

Methods:

Nationally representative annual cross sectional survey of HIV-infected adults receiving medical care in the United States, 2009-2012 data cycles. Using data from 18,095 participants, we assessed percentages prescribed ART regimens based on medical record documentation and the associations between ART regimens and viral suppression (most recent viral load test <200 copies/ml in past year) and ART-related side effects.

Results:

Among HIV-infected adults receiving medical care in the United States, 91.8% were prescribed ART; median time since ART initiation to interview date was 9.8 years. The percentage prescribed ART was significantly higher in 2012 compared to 2009 (92.7% vs 88.7%; p < 0.001). Of those prescribed ART, 51.6% were prescribed recommended initial regimens, 6.1% alternative initial regimens, 29.0% not-recommended as initial regimens, and 13.4% other regimens. Overall, 79.5% achieved viral suppression and 15.7% reported side effects. Of those prescribed ART and initiated ART in the past year, 80.5% were prescribed recommended initial regimens.

Conclusion:

Among persons prescribed ART, the majority were prescribed recommended initial regimens. Monitoring of ART use should be continued to provide ongoing assessments of ART effectiveness and tolerability in the United States.

A Novel PBPK Modeling Approach to Assess Cytochrome P450 Mediated Drug-Drug Interaction Potential of the Cytotoxic Prodrug Evofosfamide

Evofosfamide is a cytotoxic small‐molecule prodrug preferentially activated under hypoxic conditions. The cytotoxicity of evofosfamide impacted the generation of in vitro drug‐drug interaction (DDI) data, especially in vitro induction results. Therefore, a novel physiologically based pharmacokinetic (PBPK) approach was used, which involved available in vitro and clinical data of evofosfamide and combined it with induction data from the prototypical cytochrome P450 (CYP)3A inducer rifampicin. The area under the concentration‐time curve (AUC) ratios of midazolam were above 0.80, indicating that induction of CYP3A by evofosfamide administered weekly is unlikely to occur in humans. Moreover, static and PBPK modeling showed no clinically relevant inhibition via CYP2B6, CYP2D6, and CYP3A4. In conclusion, PBPK models were used to supplement in vitro information of a cytotoxic compound. This approach may set a precedent for future studies of cytotoxic drugs, potentially reducing the need for clinical DDI studies and providing more confidence in the clinical use of approved cytotoxic compounds for which DDI information is sparse.

Challenges and recent progress in drug discovery for tropical diseases

Infectious tropical diseases have a huge effect in terms of mortality and morbidity, and impose a heavy economic burden on affected countries. These diseases predominantly affect the world's poorest people. Currently available drugs are inadequate for the majority of these diseases, and there is an urgent need for new treatments. This Review discusses some of the challenges involved in developing new drugs to treat these diseases and highlights recent progress. While there have been notable successes, there is still a long way to go.

Analysis of drug-drug interactions among patients receiving antiretroviral regimens using data from a large open-source prescription database

PURPOSE

Results of a study of contraindicated concomitant medication use among recipients of preferred antiretroviral therapy (ART) regimens are reported.

METHODS

A retrospective study was conducted to evaluate concomitant medication use in a cohort of previously treatment-naive, human immunodeficiency virus (HIV)-infected U.S. patients prescribed preferred ART regimens during the period April 2014-March 2015. Data were obtained from a proprietary longitudinal prescription database; elements retrieved included age, sex, and prescription data. The outcome of interest was the frequency of drug-drug interactions (DDIs) associated with concomitant use of contraindicated medications.

RESULTS

Data on 25,919 unique treatment-naive patients who used a preferred ART regimen were collected. Overall, there were 384 instances in which a contraindicated medication was dispensed for concurrent use with a recommended ART regimen. Rates of contraindicated concomitant medication use differed significantly by ART regimen; the highest rate (3.2%) was for darunavir plus ritonavir plus emtricitabine-tenofovir disoproxil fumarate (DRV plus RTV plus FTC/TDF), followed by elvitegravir-cobicistat-emtricitabine-tenofovir disoproxil fumarate (EVG/c/FTC/TDF)(2.8%). The highest frequencies of DDIs were associated with ART regimens that included a pharmacoenhancing agent: DRV plus RTV plus FTC/TDF (3.2%) and EVG/c/FTC/TDF (2.8%).

CONCLUSION

In a large population of treatment-naive HIV-infected patients, ART regimens that contained a pharmacoenhancing agent were involved most frequently in contraindicated medication-related DDIs. All of the DDIs could have been avoided by using therapeutic alternatives within the same class not associated with a DDI.

Antiretroviral therapy in geriatric HIV patients: the GEPPO cohort study

Background

GEPPO is a prospective observational multi-centric cohort including HIV-infected geriatric patients. We hypothesized that the GEPPO cohort may help characterize antiretroviral (ARV) prescribing criteria used in real life by Italian infectious disease (ID) physicians.

Methods

This was a cross-sectional study describing the current ARV regimen in a geriatric HIV population (≥65 years). Antiretroviral strategies were categorized as follows: (i) multidrug regimens (MDRs), which comprised triple or mega ART combinations; (ii) less drug regimens (LDRs), which comprised fewer than three ART compounds. Multi-morbidity (MM) was defined as the presence of three or more non-communicable diseases, and polypharmacy (PP) as the use of five or more medications in chronic use. Four alternative combinations (MM+PP+, MM+PP-, MM-PP+, MM-PP-) were used in logistic regression analyses.

Results

A total of 1222 HIV-positive patients were included (median age 70 years). Females composed 16% of the cohort. Median duration of HIV infection was 17 years; 335 population members had been infected for >20 years. MM was present in 64% and PP in 37% of the patients. Treatment consisted of triple therapy in 66.4%, dual therapy in 25.3%, monotherapy in 6.5% and 'mega-ART' with more than three drugs in 1.64% of the patients. In multivariate logistic regression MM and PP were predictive for mono-dual, NRTI-sparing and tenofovir disoproxil fumarate (TDF)-sparing combinations. Female gender and age were predictors of unboosted ARV regimens.

Conclusions

High prevalence of non-conventional ARV regimens in elderly HIV patients suggests that clinicians try to tailor ARV regimens according to age, HIV duration, MM and PP.

Pharmacokinetic Drug-Drug Interactions Between Immunosuppressant and Anti-Infective Agents: Antimetabolites and Corticosteroids

Infections account for 15–20% of deaths in transplant recipients, requiring rapid and appropriate therapeutic interventions. Many anti-infective agents interact with immunosuppressive regimens used in transplantation, placing patients at increased risk for adverse drug reactions and prolonged hospitalizations. There is established data regarding the level of evidence and magnitude of interactions between calcineurin inhibitors and mammalian target of rapamycin inhibitors with anti-infective agents. Less is known about the interactions with anti-proliferative agents and corticosteroids, with gaps in knowledge on the appropriate management of these interactions. The objective of this review was to highlight the pharmacokinetic drug–drug interactions between antimetabolites and corticosteroids with commonly used anti-infective agents.

Statin drug interactions and related adverse reactions: an update

INTRODUCTION

Statins reduce the risk of cardiovascular morbidity and mortality in patients with or at risk for cardiovascular disease and their use is expanding, especially in elderly. Statins are prescribed on a long-term basis and may undergo drug-drug interactions (DDIs) with other drugs. Statins have different safety and tolerability, and this might affect the possibility of DDIs with other cardiovascular drugs, increasing the risk of statin-associated myopathy and hepatotoxicity. Polypharmacy and pharmacogenetic variability are potential causes of statin DDIs. Thus, the safety and adverse effects of statins, particularly in patients receiving multiple medications at risk of DDIs, are a matter of special concern.

AREAS COVERED

The purpose of this manuscript is to give an update on the potential statin DDIs and related adverse drug reactions (myopathy and hepatotoxicity), with special considerations on polypharmacy in elderly population, HIV patients, cardiovascular drugs and liver toxicities. The potential DDIs among statins and monoclonal antibodies including the recently approved PCSK9 inhibitors are also extensively discussed in the present review.

EXPERT OPINION

A better understanding of the incidence and clinical significance of statin DDIs will help physicians in fine-tuning the lipid-lowering therapeutic interventions thus providing their patients with an evidence-based, safe and cost-effective clinical support.

Effects of antiretroviral treatment and nadir CD4 count in progression to cardiovascular events and related comorbidities in a HIV Brazilian cohort: a multi-stage approach

The use of highly active antiretroviral therapy has resulted in changes of comorbidity profile in people living with HIV (PLHIV), increasing non-AIDS-related events. The occurrence of cardiovascular events is greater in PLHIV, but the mechanism responsible for it is still controversial. This article aimed to investigate factors associated with the progression to cardiovascular events in PLHIV using HAART. A 15-years cohort study with 1135 PLHIV was conducted in Rio de Janeiro-Brazil. Clinical progression was stratified in five states: No comorbidities (s₁), arterial hypertension (s₂), lipid abnormalities (s₃), hypertension and lipid abnormalities (s₄) and major cardiovascular events (stroke, coronary artery disease, thrombosis or death) (s₅). Semi-Markov models evaluated the effects of cardiovascular traditional factors, treatment and clinical covariates on transitions between these states. Hazard Ratios (HR) and 95% confidence intervals (CI) were provided. In addition to traditional factors (age, sex, educational level and skin color), the development of one comorbidity (lipid abnormalities or hypertension) increased in patients with low nadir CD4 (<50 cells/mm³), (HR = 1.59, CI 1.11-2.28 and 1.36, CI 1.11-1.66, respectively). The risk to experience a second comorbidity (s₃→s₄) increased 75% with low nadir CD4. Age was the only factor that increased the risk of major cardiovascular events once having lipid abnormalities with or without hypertension (s₃,s₄→s₅). The prolonged use of certain antiretroviral drugs (abacavir, didanosine, ritonavir, lopinavir, amprenavir and fosamprenavir) increased the risk of direct transition (s₁→s₅) to major cardiovascular events (HR = 5.29, CI 1.16-24.05). This analysis suggests that prolonged use of certain antiretroviral drugs led directly to major cardiovascular events, while low nadir CD4 only affected the occurrence of lipid abnormalities and hypertension. Management strategies, including rational use of complex exams (such as, computed-tomography angiography), statins and antihypertensives, should be developed based on the distinct roles of antiretroviral use and of HIV infection itself on the progression to cardiovascular events.

Inhibition of human cytochromes P450 in vitro by ritonavir and cobicistat

OBJECTIVES

Ritonavir and cobicistat are strong inhibitors of human cytochrome P450-3A (CYP3A) isoforms, and are used clinically as pharmacokinetic boosting agents for other antiretroviral drugs. Data reported by the manufacturer suggest that cobicistat is a more selective inhibitor of CYP3A than ritonavir. However, this claim has not been validated in clinical studies. This study evaluated the in-vitro inhibitory potency of ritonavir and cobicistat vs a series of human CYP isoforms.

METHOD

The model system utilized human liver microsomes and isoform-selective index substrates.

KEY FINDINGS

Ritonavir and cobicistat both were strong inhibitors of CYP3A4, with IC₅₀ values of 0.014 and 0.032 μm, respectively. A component of inhibition was time-dependent (mechanism-based). Neither drug meaningfully inhibited CYP1A2 (IC₅₀  > 150 μm). CYP2B6, CYP2C9, CYP2C19 and CYP2D6 were inhibited by both drugs, but with IC₅₀ values exceeding 6 μm.

CONCLUSIONS

Consistent with previous reports, both ritonavir and cobicistat were highly potent inhibitors of CYP3A. Both drugs were weaker inhibitors of other human CYPs, with IC₅₀ values at least two orders of magnitude higher. There was no evidence of a meaningful difference in selectivity between the two drugs.

Interaction of Rifampin and Darunavir-Ritonavir or Darunavir-Cobicistat In Vitro

Treatment of HIV-infected patients coinfected with Mycobacterium tuberculosis is challenging due to drug-drug interactions (DDIs) between antiretrovirals (ARVs) and antituberculosis (anti-TB) drugs. The aim of this study was to quantify the effect of cobicistat (COBI) or ritonavir (RTV) in modulating DDIs between darunavir (DRV) and rifampin (RIF) in a human hepatocyte-based in vitro model. Human primary hepatocyte cultures were incubated with RIF alone or in combination with either COBI or RTV for 3 days, followed by coincubation with DRV for 1 h. The resultant DRV concentrations were quantified by high-performance liquid chromatography with UV detection, and the apparent intrinsic clearance (CL_int.app.) of DRV was calculated. Both RTV and COBI lowered the RIF-induced increases in CL_int.app. in a concentration-dependent manner. Linear regression analysis showed that log₁₀ RTV and log₁₀ COBI concentrations were associated with the percent inhibition of RIF-induced elevations in DRV CL_int.app., where β was equal to -234 (95% confidence interval [CI] = -275 to -193; P < 0.0001) and -73 (95% CI = -89 to -57; P < 0.0001), respectively. RTV was more effective in lowering 10 μM RIF-induced elevations in DRV CL_int.app. (half-maximal [50%] inhibitory concentration [IC₅₀] = 0.025 μM) than COBI (IC₅₀ = 0.223 μM). Incubation of either RTV or COBI in combination with RIF was sufficient to overcome RIF-induced elevations in DRV CL_int.app., with RTV being more potent than COBI. These data provide the first in vitro experimental insight into DDIs between RIF and COBI-boosted or RTV-boosted DRV and will be useful to inform physiologically based pharmacokinetic (PBPK) models to aid in optimizing dosing regimens for the treatment of patients coinfected with HIV and M. tuberculosis.

Alterations in cellular pharmacokinetics and pharmacodynamics of elvitegravir in response to ethanol exposure in HIV-1 infected monocytic (U1) cells

Ethanol consumption is negatively associated with antiretroviral therapy (ART) adherence and general health in HIV positive individuals. Previously, we demonstrated ethanol-mediated alterations to metabolism of elvitegravir (EVG) in human liver microsomes. In the current study, we investigated ethanol influence on the pharmacokinetic and pharmacodynamic interactions of EVG in HIV infected monocytic (U1) cells. U1 cells were treated with 5 μM EVG, 2 μM Cobicistat (COBI), a booster drug, and 20 mM ethanol for up to 24 hours. EVG, HIV p24 levels, alterations in cytochrome P450 (CYP) 3A4, MRP1, and MDR1 protein expressions were measured. Presence of ethanol demonstrated a significant effect on the total exposures of both EVG and EVG in combination with COBI. Ethanol also increased the HIV replication despite the presence of drugs and this elevated HIV replication was reduced in the presence of MRP1 and MDR1 inhibitors. Consequently, a slight increase in EVG concentration was observed in the presence of MRP1 inhibitor but not with MDR1 inhibitor. Furthermore, CYP3A4, MRP1 and MDR1 protein levels were significantly induced in treatment groups which included ethanol compared to those with no treatment. In summary, these findings suggest that Ethanol reduces intra cellular EVG exposure by modifying drug metabolism and transporter protein expression. This study provides valuable evidence for further investigation of ethanol effects on the intracellular concentration of EVG in ex vivo or in vivo studies.

Meal Effects Confound Attempts to Counteract Rabeprazole-Induced Hypochlorhydria Decreases in Atazanavir Absorption

PURPOSE

Clinically relevant pharmacokinetic interactions exist between gastric acid-reducing agents and certain weakly basic drugs that rely on acidic environments for optimal oral absorption. In this study, we examine whether the administration of betaine hydrochloride under fed conditions can enhance the absorption of atazanavir, an HIV-1 protease inhibitor, during pharmacologically-induced hypochlorhydria.

METHODS

In this randomized, single-dose, 3 period, crossover study healthy volunteers received ritonavir-boosted atazanavir (atazanavir/ritonavir 300/100 mg) alone, following pretreatment with the proton pump inhibitor rabeprazole (20 mg twice daily), and with 1500 mg of betaine HCl after rabeprazole pretreatment. Atazanavir was administered with a light meal and gastric pH was monitored using the Heidelberg Capsule.

RESULTS

Pretreatment with rabeprazole resulted in significant reductions in atazanavir C_max (p < 0.01) and AUC_0-last (p < 0.001) (71 and 70%, respectively), and modest decreases in ritonavir C_max and AUC_last (p < 0.01) (40% and 41%, respectively). The addition of betaine HCl restored 13% of ATV C_max and 12% of AUC_last lost due to rabeprazole.

CONCLUSIONS

The co-administration of rabeprazole with atazanavir resulted in significant decreases in atazanavir exposure. The addition of betaine HCl did not sufficiently mitigate the loss of ATV exposure observed during RAB-induced hypochlorhydria. Meal effects lead to a marked difference in the outcome of betaine HCl on atazanavir exposure than we previously reported for dasatanib under fasting conditions.

Chronic Effects of Ethanol and/or Darunavir/Ritonavir on U937 Monocytic Cells: Regulation of Cytochrome P450 and Antioxidant Enzymes, Oxidative Stress, and Cytotoxicity

BACKGROUND

Our recent study has shown that acute treatment with ethanol (EtOH) increases oxidative stress and cytotoxicity through cytochrome P450 2E1 (CYP2E1)-mediated pathway in U937 monocytic cells. U937 cells are derived from blood monocytes and are considered as the model system for HIV-related study. Since the prevalence of alcohol use in HIV-infected population is high, and HIV+ patients are on antiretroviral therapy (ART) soon after they are diagnosed, it is important to study the interactions between EtOH and ART in monocytes.

METHODS

This study examined the chronic effects of EtOH and ART (darunavir/ritonavir), alone and in combination, on expression/levels of cytochrome P450 enzymes (CYPs), antioxidant enzymes (AOEs), reactive oxygen species (ROS), and cytotoxicity in U937 cells. The mRNA and protein levels were measured using quantitative reverse transcription polymerase chain reaction and Western blot, respectively. ROS and cytotoxicity were measured using flow cytometry and cell viability assay, respectively.

RESULTS

While chronic ART treatment increased CYP2E1 protein expression by 2-fold, EtOH and EtOH+ART increased CYP2E1 by ~5-fold. In contrast, ART and EtOH treatments decreased CYP3A4 protein expression by 38 ± 17% and 74 ± 15%, respectively, and the combination additively decreased CYP3A4 level by 90 ± 8%. Expressions of superoxide dismutase 1 (SOD1) and peroxiredoxin (PRDX6) were decreased by both EtOH and ART, however, the expressions of SOD2 and catalase were unaltered. These results suggested increased EtOH metabolism, increased ART accumulation, and decreased defense against ROS. Therefore, we determined the effects of EtOH and ART on ROS and cytotoxicity. While ART showed a slight increase, EtOH and EtOH+ART displayed significant increase in ROS and cytotoxicity. Moreover, the combination showed additive effects on ROS and cytotoxicity.

CONCLUSIONS

These results suggest that chronic EtOH, in the absence and presence of ART, increases ROS and cytotoxicity in monocytes, perhaps via CYP- and AOE-mediated pathways. This study has clinical implications in HIV+ alcohol users who are on ART.

Traditional Preparations and Methanol Extracts of Medicinal Plants from Papua New Guinea Exhibit Similar Cytochrome P450 Inhibition

The hypothesis underlying this current work is that fresh juice expressed from Papua New Guinea (PNG) medicinal plants (succus) will inhibit human Cytochrome P450s (CYPs). The CYP inhibitory activity identified in fresh material was compared with inhibition in methanol extracts of dried material. Succus is the most common method of traditional medicine (TM) preparation for consumption in PNG. There is increasing concern that TMs might antagonize or complicate drug therapy. We have previously shown that methanol extracts of commonly consumed PNG medicinal plants are able to induce and/or inhibit human CYPs in vitro. In this current work plant succus was prepared from fresh plant leaves. Inhibition of three major CYPs was determined using human liver microsomes and enzyme-selective model substrates. Of 15 species tested, succus from 6/15 was found to inhibit CYP1A2, 7/15 inhibited CYP3A4, and 4/15 inhibited CYP2D6. Chi-squared tests determined differences in inhibitory activity between succus and methanol preparations. Over 80% agreement was found. Thus, fresh juice from PNG medicinal plants does exhibit the potential to complicate drug therapy in at risk populations. Further, the general reproducibility of these findings suggests that methanol extraction of dried material is a reasonable surrogate preparation method for fresh plant samples.

Investigational protease inhibitors as antiretroviral therapies

INTRODUCTION

Highly Active Antiretroviral Therapy (HAART) has tremendously improved the life expectancy of the HIV-infected population over the past three decades. Protease inhibitors have been one of the major classes of drugs in HAART regimens that are effective in treating HIV. However, the emergence of resistance and cross-resistance against protease inhibitors encourages researchers to develop new PIs with broad-spectrum activity, as well as novel means of enhancing the efficacy of existing PIs.

AREAS COVERED

In this article we discuss recent advances in HIV protease inhibitor (PI) development, focusing on both investigational and experimental agents. We also include a section on pharmacokinetic booster drugs for improved bioavailability of protease inhibitors. Further, we discuss novel drug delivery systems using a variety of nanocarriers for the delivery of PIs across the blood-brain barrier to treat the HIV in the brain.

EXPERT OPINION

We discuss our opinion on the promises and challenges on the development of novel investigational and experimental PIs that are less toxic and more effective in combating drug-resistance. Further, we discuss the future of novel nanocarriers that have been developed to deliver PIs to the brain cells. Although these are promising findings, many challenges need to be overcome prior to making them a viable option.

Evaluating the role of atazanavir/cobicistat and darunavir/cobicistat fixed-dose combinations for the treatment of HIV-1 infection

Atazanavir/cobicistat (ATV/c) and darunavir/cobicistat (DRV/c) are newly approved once daily fixed-dose protease inhibitor combinations for the treatment of HIV-1 infection. Studies in healthy volunteers have established bioequivalence between cobicistat and ritonavir as pharmacoenhancers of both atazanavir (ATV) and darunavir (DRV). In addition, two randomized clinical trials (one Phase II and one Phase III noninferiority trial with a 144-week followup period) demonstrated that cobicistat had sustainable and comparable efficacy and safety to ritonavir as a pharmacoenhancer of ATV through 144 weeks of treatment in HIV-1-infected patients. Furthermore, one Phase III, open-label, single-arm, clinical trial reflected virologic and immunologic responses and safety outcomes consistent with prior published data for DRV/ritonavir 800/100 mg once daily, supporting the use of DRV/c 800/150 mg once daily for future treatment of treatment-naïve and -experienced HIV-1-infected patients with no DRV resistance-associated mutations. Low rates of virologic failure secondary to resistance to antiretroviral regimens were present in these clinical studies. Most notable adverse events in the ATV studies were hyperbilirubinemia and in the DRV study rash. Small increases in serum creatinine and minimally reduced estimated glomerular filtration rate Cockcroft-Gault calculation (eGFRCG) were observed in ATV/c and DRV/c clinical studies consistent with other studies evaluating elvitegravir/cobicistat/tenofovir/emtricitabine for the treatment of HIV-1 infection. These renal parameter changes occurred acutely in the first few weeks and plateaued off for the remaining study periods and are not necessarily clinically relevant. Cobicistat has numerous advantages compared to ritonavir such as fewer drug-drug interactions, being devoid of anti-HIV-1 activity, as well as it has better solubility affording coformulation with other antiretrovirals as simplified fixed-dose combinations. Overall, the recent approval of ATV/c and DRV/c offers HIV patients opportunities for improved adherence to lifelong treatment. Future studies are warranted to determine the efficacy and safety of ATV/c and DRV/c in treatment-experienced patients.

Darunavir: a review of its use in the management of HIV-1 infection

The latest HIV-1 protease inhibitor (PI) darunavir (Prezista™) has a high genetic barrier to resistance development and is active against wild-type HIV and HIV strains no longer susceptible to some older PIs. Ritonavir-boosted darunavir, as a component of antiretroviral therapy (ART), is indicated for the treatment of HIV-1 infection in adult and paediatric patients (aged ≥3 years), with or without treatment experience (details vary depending on region of approval). Several open-label or partially-blinded trials have evaluated the efficacy of ritonavir-boosted darunavir ART regimens for up to 192 weeks in these settings. In treatment-naïve adults, once-daily boosted darunavir was no less effective in establishing virological suppression than once- or twice-daily boosted lopinavir, yet was more effective at maintaining suppression long term. Moreover, treatment-experienced adults with no darunavir resistance-associated mutations (RAMs) had no less effective viral load suppression with once-daily than with twice-daily boosted darunavir. In treatment-experienced adults, including some with multiple major PI RAMs, twice-daily boosted darunavir was more effective than twice-daily boosted lopinavir or boosted control PIs in reducing viral load, and provided virological benefit as part of a salvage regimen in those with few remaining treatment options. Boosted darunavir also reduced viral load when administered once-daily in treatment-naïve adolescents or twice-daily in treatment-experienced children and adolescents. Boosted darunavir is generally well tolerated, with gastrointestinal disturbances and lipid abnormalities among the most common tolerability issues. It has a lipid profile more favourable than that of boosted lopinavir in terms of total cholesterol and triglyceride changes and, when administered once daily, its lipid effects are generally similar to those of boosted atazanavir. Thus, boosted darunavir is a useful option for the ART regimens of adult and paediatric patients with HIV-1 infection.

Drug-drug interactions between anti-retroviral therapies and drugs of abuse in HIV systems

INTRODUCTION

Substance abuse is a common problem among HIV-infected individuals. Importantly, addictions as well as moderate use of alcohol, smoking, or other illicit drugs have been identified as major reasons for non-adherence to antiretroviral therapy (ART) among HIV patients. The literature also suggests a decrease in the response to ART among HIV patients who use these substances, leading to failure to achieve optimal virological response and increased disease progression.

AREAS COVERED

This review discusses the challenges with adherence to ART as well as observed drug interactions and known toxicities with major drugs of abuse, such as alcohol, smoking, methamphetamine, cocaine, marijuana, and opioids. The lack of adherence and drug interactions potentially lead to decreased efficacy of ART drugs and increased ART, and drugs of abuse-mediated toxicity. As CYP is the common pathway in metabolizing both ART and drugs of abuse, we discuss the possible involvement of CYP pathways in such drug interactions.

EXPERT OPINION

We acknowledge that further studies focusing on common metabolic pathways involving CYP and advance research in this area would help to potentially develop novel/alternate interventions and drug dose/regimen adjustments to improve medication outcomes in HIV patients who consume drugs of abuse.

A randomized trial in healthy subjects to assess the bioequivalence of an atazanavir/cobicistat fixed-dose combination tablet versus administration as separate agents

BACKGROUND

Cobicistat (COBI) is an alternative pharmacoenhancer to ritonavir. A fixed-dose combination (FDC) tablet containing atazanavir (ATV) and COBI has been developed for the treatment of HIV-1-infected patients.

METHODS

This open-label, single-centre, single-dose, crossover study, randomized 64 healthy subjects to one of eight treatment sequences. Under light meal conditions, maximum plasma concentration (Cmax), area under the plasma concentration-time curve (AUC) to infinity (AUCINF) and AUC to the last measurable concentration (AUC0-T) for ATV and COBI administered as an FDC of ATV/COBI (300/150 mg) were compared to those following administration as separate agents given together; bioequivalence was concluded if the 90% CIs of the geometric mean ratios fell within the predetermined range of 0.80, 1.25. ATV and COBI pharmacokinetic parameters following administration as the FDC or as separate agents were also compared under fasted conditions. The effect of food (light and high-fat meals) on the pharmacokinetics of ATV and COBI for the FDC was also assessed.

RESULTS

ATV and COBI administered in an FDC tablet were bioequivalent to the individual agents when given with a light meal. Under fasted conditions, pharmacokinetic parameters for ATV and COBI were similar for the individual components and the FDC. For the FDC, systemic exposure to ATV increased with a light meal compared to fasted conditions, and ATV concentration 24 h post-dose was similar with a light meal compared with a high-fat meal.

CONCLUSIONS

ATV/COBI (300/150 mg) FDC tablet was bioequivalent to coadministration as separate agents with a light meal in healthy subjects. Clinicaltrials.gov identifier NCT01837719.

Ombitasvir (ABT-267), a novel NS5A inhibitor for the treatment of hepatitis C

INTRODUCTION

Chronic hepatitis C infection is a global disease with 160 million people infected worldwide. Until recently, therapy was characterized by long duration, suboptimal success rates and significant adverse drug reactions. The development of direct-acting antivirals initiated a dramatic change in the treatment of hepatitis C.

AREAS COVERED

This review covers the development of the novel NS5A inhibitor ombitasvir (ABT-267) and its clinical evaluation in Phase I to III trials as monotherapy and in combination with the NS3/4A inhibitor ABT-450/r and the non-nucleoside NS5B inhibitor dasabuvir (ABT-333) ± ribavirin.

EXPERT OPINION

Ombitasvir (ABT-267) is a potent inhibitor of the hepatitis C virus protein NS5A, has favorable pharmacokinetic characteristics and is active in the picomolar range against genotype 1 - 6. In patients with genotype 1 and 4, 12-week combination treatment with ombitasvir, dasabuvir and ABT-450/r plus ribavirin was highly effective and resulted in 12-week sustained virological response rates higher than 95% in treatment-naöve and treatment-experienced patients. In liver transplant recipients with genotype 1 hepatitis C, success rates in the same range can be expected after 24 weeks of treatment according to preliminary trial results. Genotype 1a patients with compensated cirrhosis who were prior nonresponders benefit from a treatment duration of 24 weeks.

Interactions of Papua New Guinea medicinal plant extracts with antiretroviral therapy

ETHNOPHARMACOLOGICAL RELEVANCE

A substantial proportion of the population in Papua New Guinea (PNG) lives with human immunodeficiency virus (HIV). Treatment requires lifelong use of antiretroviral therapy (ART). The majority of people in PNG use traditional medicines (TM) derived from plants for all types of health promotions. Consequently, there is a concern that herb-drug interactions may impact the efficacy of ART. Herb-drug, or drug-drug, interactions occur at the level of metabolism through two major mechanisms: enzyme induction or enzyme inhibition. In this study, extracts of commonly-used medicinal plants from PNG were screened for herb-drug interactions related to cytochrome P450s (CYPs).

MATERIALS AND METHODS

Sixty nine methanol extracts of TM plants were screened for their ability to induce CYPs by human aryl hydrocarbon receptor- (hAhR-) and human pregnane X receptor- (hPXR-) dependent mechanisms, utilizing a commercially available cell-based luciferase reporter system. Inhibition of three major CYPs, CYP1A2, CYP3A4, and CYP2D6, was determined using human liver microsomes and enzyme-selective model substrates.

RESULTS

Almost one third of the TM plant extracts induced the hAhR-dependent expression of CYP1A2, the hPXR-dependent expression of CYP3A4, or both. Almost two thirds inhibited CYP1A2, CYP3A4, or CYP2D6, or combinations thereof. Many plant extracts exhibited both induction and inhibition properties.

CONCLUSIONS

We demonstrated that the potent and selective ability of extracts from PNG medicinal plants to affect drug metabolizing enzymes through induction and/or inhibition is a common phenomenon. Use of traditional medicines concomitantly with ART could dramatically alter the concentrations of antiretroviral drugs in the body; and their efficacy. PNG healthcare providers should counsel HIV patients because of this consequence.

Clinically relevant drug-drug interactions between antiretrovirals and antifungals

INTRODUCTION

Complete delineation of the HIV-1 life cycle has resulted in the development of several antiretroviral drugs. Twenty-five therapeutic agents belonging to five different classes are currently available for the treatment of HIV-1 infections. Advent of triple combination antiretroviral therapy has significantly lowered the mortality rate in HIV patients. However, fungal infections still represent major opportunistic diseases in immunocompromised patients worldwide.

AREAS COVERED

Antiretroviral drugs that target enzymes and/or proteins indispensable for viral replication are discussed in this article. Fungal infections, causative organisms, epidemiology and preferred treatment modalities are also outlined. Finally, observed/predicted drug-drug interactions between antiretrovirals and antifungals are summarized along with clinical recommendations.

EXPERT OPINION

Concomitant use of amphotericin B and tenofovir must be closely monitored for renal functioning. Due to relatively weak interactive potential with the CYP450 system, fluconazole is the preferred antifungal drug. High itraconazole doses (> 200 mg/day) are not advised in patients receiving booster protease inhibitor (PI) regimen. Posaconazole is contraindicated in combination with either efavirenz or fosamprenavir. Moreover, voriconazole is contraindicated with high-dose ritonavir-boosted PI. Echinocandins may aid in overcoming the limitations of existing antifungal therapy. An increasing number of documented or predicted drug-drug interactions and therapeutic drug monitoring may aid in the management of HIV-associated opportunistic fungal infections.

Role of P-glycoprotein in the distribution of the HIV protease inhibitor atazanavir in the brain and male genital tract

The blood-testis barrier and blood-brain barrier are responsible for protecting the male genital tract and central nervous system from xenobiotic exposure. In HIV-infected patients, low concentrations of antiretroviral drugs in cerebrospinal fluid and seminal fluid have been reported. One mechanism that may contribute to reduced concentrations is the expression of ATP-binding cassette drug efflux transporters, such as P-glycoprotein (P-gp). The objective of this study was to investigate in vivo the tissue distribution of the HIV protease inhibitor atazanavir in wild-type (WT) mice, P-gp/breast cancer resistance protein (Bcrp)-knockout (Mdr1a-/-, Mdr1b-/-, and Abcg2-/- triple-knockout [TKO]) mice, and Cyp3a-/- (Cyp) mice. WT mice and Cyp mice were pretreated with a P-gp/Bcrp inhibitor, elacridar (5 mg/kg of body weight), and the HIV protease inhibitor and boosting agent ritonavir (2 mg/kg intravenously [i.v.]), respectively. Atazanavir (10 mg/kg) was administered i.v. Atazanavir concentrations in plasma (Cplasma), brain (Cbrain), and testes (Ctestes) were quantified at various times by liquid chromatography-tandem mass spectrometry. In TKO mice, we demonstrated a significant increase in atazanavir Cbrain/Cplasma (5.4-fold) and Ctestes/Cplasma (4.6-fold) ratios compared to those in WT mice (P<0.05). Elacridar-treated WT mice showed a significant increase in atazanavir Cbrain/Cplasma (12.3-fold) and Ctestes/Cplasma (13.5-fold) ratios compared to those in vehicle-treated WT mice. In Cyp mice pretreated with ritonavir, significant (P<0.05) increases in atazanavir Cbrain/Cplasma (1.8-fold) and Ctestes/Cplasma (9.5-fold) ratios compared to those in vehicle-treated WT mice were observed. These data suggest that drug efflux transporters, i.e., P-gp, are involved in limiting the ability of atazanavir to permeate the rodent brain and genital tract. Since these transporters are known to be expressed in humans, they could contribute to the low cerebrospinal and seminal fluid antiretroviral concentrations reported in the clinic.

Approaches to the synthesis of a novel, anti-HIV active integrase inhibitor

The novel HIV-1 integrase inhibitor 1, discovered in our laboratory, exhibits potent anti-HIV activity against a diverse set of HIV-1 isolates and also against HIV-2 and SIV. In addition, this compound displays low cellular cytotoxicity and possesses a favorable in vitro drug interaction profile with respect to isozymes of cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT). However, the total synthesis of this significant HIV integrase inhibitor has not been reported. This contribution describes an optimized, reproducible, multi-step, synthetic route to inhibitor 1. The yield for the separate steps averaged about 80%. The methodologies utilized in the synthesis were, among others, a palladium-catalyzed cross-coupling reaction, a crossed-Claisen condensation, and a hydrazino amide synthesis step. Successful alternative synthetic methodologies for some of the steps are also described.

Evaluation of the pharmacokinetics and drug interactions of the two recently developed statins, rosuvastatin and pitavastatin

INTRODUCTION

Statins are the cornerstone of lipid-lowering therapy to reduce the risk of coronary heart disease. Rosuvastatin and pitavastatin are the two recently developed statins with less potential for drug interaction resulting in improved safety profiles.

AREAS COVERED

This review summarizes the pharmacokinetics and drug interactions of rosuvastatin and pitavastatin. The materials reviewed were identified by searching PubMed for publications using 'rosuvastatin', 'pitavastatin', 'statins', 'pharmacokinetics' and 'drug interaction' as the search terms.

EXPERT OPINION

Rosuvastatin and pitavastatin have favorable pharmacokinetic and safety profiles as their disposition does not depend on or is only marginally influenced by cytochrome P450 (CYP) enzymes, thus potentially reducing the risk of drug-drug interactions of these two statins with other drugs known to inhibit CYP enzymes. However, drug transporters play a significant role in the disposition of rosuvastatin and pitavastatin and drug interactions may occur through these. Genetic polymorphisms in drug transporters may also affect the pharmacokinetics, drug interactions and/or the lipid-lowering effect of these statins to a different extent.

[Consensus Statement by GeSIDA/National AIDS Plan Secretariat on antiretroviral treatment in adults infected by the human immunodeficiency virus (Updated January 2013)]

OBJECTIVE

This consensus document is an update of combined antiretroviral therapy (cART) guidelines for HIV-1 infected adult patients.

METHODS

To formulate these recommendations a panel composed of members of the GeSIDA/National AIDS Plan Secretariat (Grupo de Estudio de Sida and the Secretaría del Plan Nacional sobre el Sida) reviewed the efficacy and safety advances in clinical trials, cohort and pharmacokinetic studies published in medical journals (PubMed and Embase) or presented in medical scientific meetings. The strength of the recommendations and the evidence which support them are based on a modification of the criteria of Infectious Diseases Society of America.

RESULTS

cART is recommended in patients with symptoms of HIV infection, in pregnant women, in serodiscordant couples with high risk of transmission, in hepatitisB co-infection requiring treatment, and in HIV nephropathy. cART is recommended in asymptomatic patients if CD4 is <500cells/μl. If CD4 are >500cells/μl cART should be considered in the case of chronic hepatitisC, cirrhosis, high cardiovascular risk, plasma viral load >100.000 copies/ml, proportion of CD4 cells <14%, neurocognitive deficits, and in people aged >55years. The objective of cART is to achieve an undetectable viral load. The first cART should include 2 reverse transcriptase inhibitors (RTI) nucleoside analogs and a third drug (a non-analog RTI, a ritonavir boosted protease inhibitor, or an integrase inhibitor). The panel has consensually selected some drug combinations, for the first cART and specific criteria for cART in acute HIV infection, in tuberculosis and other HIV related opportunistic infections, for the women and in pregnancy, in hepatitisB or C co-infection, in HIV-2 infection, and in post-exposure prophylaxis.

CONCLUSIONS

These new guidelines update previous recommendations related to first cART (when to begin and what drugs should be used), how to monitor, and what to do in case of viral failure or adverse drug reactions. cART specific criteria in comorbid patients and special situations are similarly updated.

Polypharmacy and risk of antiretroviral drug interactions among the aging HIV-infected population

BACKGROUND

Among aging HIV-infected adults, polypharmacy and its consequences have not been well-described.

OBJECTIVE

To characterize the extent of polypharmacy and the risk of antiretroviral (ARV) drug interactions among persons of different ages.

DESIGN AND PARTICIPANTS

Cross-sectional analysis among patients within the HIV Outpatient Study (HOPS) cohort who were prescribed ARVs during 2006-2010.

MAIN MEASURES

We used the University of Liverpool HIV drug interactions database to identify ARV/non-ARV interactions with potential for clinical significance.

KEY RESULTS

Of 3,810 patients analyzed (median age 46 years, 34 % ≥ 50 years old) at midpoint of observation, 1,494 (39 %) patients were prescribed ≥ 5 non-ARV medications: 706 (54 %) of 1,312 patients ≥ 50 years old compared with 788 (32 %) of 2,498 patients < 50 years. During the five-year period, the number of patients who were prescribed at least one ARV/non-ARV combination that was contraindicated or had moderate or high evidence of interaction was 267 (7 %) and 1,267 (33 %), respectively. Variables independently associated with having been prescribed a contraindicated ARV/non-ARV combination included older age (adjusted odds ratio [aOR] per 10 years of age 1.17, 95 % CI 1.01-1.35), anxiety (aOR 1.78, 95 % CI 1.32-2.40), dyslipidemia (aOR 1.96, 95 % CI 1.28-2.99), higher daily non-ARV medication burden (aOR 1.13, 95 % CI 1.10-1.17), and having been prescribed a protease inhibitor (aOR 2.10, 95 % CI 1.59-2.76). Compared with patients < 50 years, older patients were more likely to have been prescribed an ARV/non-ARV combination that was contraindicated (unadjusted OR 1.44, 95 % CI 1.14-1.82), or had moderate or high evidence of interaction (unadjusted OR 1.29, 95 % CI 1.15-1.44).

CONCLUSIONS

A substantial percentage of patients were prescribed at least one ARV/non-ARV combination that was contraindicated or had potential for a clinically significant interaction. As HIV-infected patients age and experience multiple comorbidities, systematic reviews of current medications by providers may reduce risk of such exposures.

Modeling of rifampicin-induced CYP3A4 activation dynamics for the prediction of clinical drug-drug interactions from in vitro data

Induction of cytochrome P450 3A4 (CYP3A4) expression is often implicated in clinically relevant drug-drug interactions (DDI), as metabolism catalyzed by this enzyme is the dominant route of elimination for many drugs. Although several DDI models have been proposed, none have comprehensively considered the effects of enzyme transcription/translation dynamics on induction-based DDI. Rifampicin is a well-known CYP3A4 inducer, and is commonly used as a positive control for evaluating the CYP3A4 induction potential of test compounds. Herein, we report the compilation of in vitro induction data for CYP3A4 by rifampicin in human hepatocytes, and the transcription/translation model developed for this enzyme using an extended least squares method that can account for inherent inter-individual variability. We also developed physiologically based pharmacokinetic (PBPK) models for the CYP3A4 inducer and CYP3A4 substrates. Finally, we demonstrated that rifampicin-induced DDI can be predicted with reasonable accuracy, and that a static model can be used to simulate DDI once the blood concentration of the inducer reaches a steady state following repeated dosing. This dynamic PBPK-based DDI model was implemented on a new multi-hierarchical physiology simulation platform named PhysioDesigner.

A novel anti-HIV active integrase inhibitor with a favorable in vitro cytochrome P450 and uridine 5'-diphospho-glucuronosyltransferase metabolism profile

Research efforts on the human immunodeficiency virus (HIV) integrase have resulted in two approved drugs. However, co-infection of HIV with Mycobacterium tuberculosis and other microbial and viral agents has introduced added complications to this pandemic, requiring favorable drug-drug interaction profiles for antiviral therapeutics targeting HIV. Cytochrome P450 (CYP) and uridine 5'-diphospho-glucuronosyltransferase (UGT) are pivotal determining factors in the occurrence of adverse drug-drug interactions. For this reason, it is important that anti-HIV agents, such as integrase inhibitors, possess favorable profiles with respect to CYP and UGT. We have discovered a novel HIV integrase inhibitor (compound 1) that exhibits low nM antiviral activity against a diverse set of HIV-1 isolates, and against HIV-2 and the simian immunodeficiency virus (SIV). Compound 1 displays low in vitro cytotoxicity and its resistance and related drug susceptibility profiles are favorable. Data from in vitro studies revealed that compound 1 was not a substrate for UGT isoforms and that it was not an inhibitor or activator of key CYP isozymes.

Statin drug interactions and related adverse reactions

INTRODUCTION

Statin monotherapy is generally well tolerated, with a low frequency of adverse events. The most important adverse effects associated with statins are myopathy and an asymptomatic increase in hepatic transaminases, both of which occur infrequently. Because statins are prescribed on a long-term basis, their possible interactions with other drugs deserve particular attention, as many patients will typically receive pharmacological therapy for concomitant conditions during the course of statin treatment.

AREAS COVERED

This review summarizes the pharmacokinetic properties of statins and emphasizes their clinically relevant drug interactions and related adverse reactions.

EXPERT OPINION

Avoiding drug-drug interactions and consequent adverse drug reactions is essential in order to optimize compliance, and thus improve the treatment of patients at high cardiovascular risk. The different pharmacokinetic profiles among statins should be carefully considered, in order to understand the possible spectrum of drug interactions. The growing trend toward earlier statin treatment for the prevention of cardiovascular disease means that physicians must anticipate future polypharmacy when their patients require additional medications for comorbid conditions.

[Consensus document of Gesida and Spanish Secretariat for the National Plan on AIDS (SPNS) regarding combined antiretroviral treatment in adults infected by the human immunodeficiency virus (January 2012)]

This consensus document has been prepared by a panel consisting of members of the AIDS Study Group (Gesida) and the Spanish Secretariat for the National Plan on AIDS (SPNS) after reviewing the efficacy and safety results of clinical trials, cohort and pharmacokinetic studies published in medical journals, or presented in medical scientific meetings. Gesida has prepared an objective and structured method to prioritise combined antiretroviral treatment (cART) in naïve patients. Recommendations strength (A, B, C) and the evidence which supports them (I, II, III) are based on a modification of the Infectious Diseases Society of America criteria. The current antiretroviral treatment (ART) of choice for chronic HIV infection is the combination of three drugs. ART is recommended in patients with symptomatic HIV infection, in pregnancy, in serodiscordant couples with high transmission risk, hepatitis B fulfilling treatment criteria, and HIV nephropathy. Guidelines on ART treatment in patients with concurrent diagnosis of HIV infection and an opportunistic type C infection are included. In asymptomatic patients ART is recommended on the basis of CD4 lymphocyte counts, plasma viral load and patient co-morbidities, as follows: 1) therapy should be started in patients with CD4 counts <350 cells/μL; 2) when CD4 counts are between 350 and 500 cells/μL, therapy will be recommended and only delayed if patient is reluctant to take it, the CD4 are stabilised, and the plasma viral load is low; 3) therapy could be deferred when CD4 counts are above 500 cells/μL, but should be considered in cases of cirrhosis, chronic hepatitis C, high cardiovascular risk, plasma viral load >10(5) copies/mL, proportion of CD4 cells <14%, and in people aged >55 years. ART should include 2 reverse transcriptase inhibitors nucleoside analogues and a third drug (non-analogue reverse transcriptase inhibitor, ritonavir boosted protease inhibitor or integrase inhibitor). The panel has consensually selected and given priority to using the Gesida score for some drug combinations, some of them co-formulated. The objective of ART is to achieve an undetectable viral load. Adherence to therapy plays an essential role in maintaining antiviral response. Therapeutic options are limited after ART failures, but an undetectable viral load may be possible nowadays. Adverse events are a fading problem of ART. Guidelines in acute HIV infection, in women, in pregnancy, and to prevent mother-to-child transmission and pre- and post-exposition prophylaxis are commented upon. Management of hepatitis B or C co-infection, other co-morbidities, and the characteristics of ART in HIV-2 infection are included.

Probable corticosteroid-induced reactivation of latent hepatitis B virus infection in an HIV-positive patient involving immune escape

We describe a patient infected with human immunodeficiency virus who possessed a serological profile suggesting a previous cleared acute hepatitis B virus (HBV) infection, including high levels of antibodies against HBV surface antigen (anti-HBs). Following the administration of inhaled glucocorticosteroids combined with protease inhibitor-based antiretroviral treatment, the patient developed an unexpected severe acute hepatitis despite persistence of anti-HBs. A genotype A2 strain emerged with 2 major mutations in the S gene, sK122R and sD144E. Molecular and biological analyses strongly suggested reactivation of a latent HBV infection. The importance and the molecular basis of these 2 epitopes in immune-escape mechanisms and host-virus interactions are discussed.

Complex drug interactions of the HIV protease inhibitors 3: effect of simultaneous or staggered dosing of digoxin and ritonavir, nelfinavir, rifampin, or bupropion

As part of a larger clinical drug-drug interaction (DDI) study aimed at in vitro to in vivo prediction of HIV protease inhibitor metabolic and transporter-based DDIs, we measured the inductive (staggered administration) and inductive plus inhibitory (simultaneously administered) effect of multiple dose ritonavir (RTV), nelfinavir (NFV), or rifampin (RIF) on the pharmacokinetics of the P-glycoprotein probe, digoxin (DIG), when administered simultaneously or staggered with the protease inhibitors or RIF. In both cases, NFV did not significantly affect DIG disposition. RTV decreased DIG renal clearance (Cl(renal)) when administered simultaneously or staggered but significantly increased DIG area under the curve from time zero to 24 h (AUC(0-24 h)) only when administered simultaneously. RIF decreased DIG AUC(0-24 h) only when RIF and DIG administration was staggered. When RIF and DIG were administered simultaneously, DIG maximal observed plasma concentration and area under the curve from time zero to 4 h were significantly increased, and DIG Cl(renal) was decreased. An unexpected and potentially clinically significant DDI was observed between DIG and the CYP2B6 probe, bupropion, which decreased DIG AUC(0-24 h) 1.6-fold and increased Cl(renal) 1.8-fold. Because this was an unexpected DDI and our studies were not specifically designed to quantify this interaction, further studies are required to confirm the interaction and understand the mechanistic basis of the DDI. In summary, RTV or NFV do not induce P-glycoprotein activity measured with DIG, and RIF does so only under staggered administration.

HCV and the hepatic lipid pathway as a potential treatment target

Atherosclerosis has been described as a liver disease of the heart [1]. The liver is the central regulatory organ of lipid pathways but since dyslipidaemias are major contributors to cardiovascular disease and type 2 diabetes rather than liver disease, research in this area has not been a major focus for hepatologists. Virus-host interaction is a continuous co-evolutionary process [2] involving the host immune system and viral escape mechanisms [3]. One of the strategies HCV has adopted to escape immune clearance and establish persistent infection is to make use of hepatic lipid pathways. This review aims to: • update the hepatologist on lipid metabolism • review the evidence that HCV exploits hepatic lipid pathways to its advantage • discuss approaches to targeting host lipid pathways as adjunctive therapy.